Programmed-cell death events during tapetum development of angiosperms

Programmed-cell-death events in the tapetum of two angiosperms (Lobivia rau schii Zecher and Tillandsia albida Mez et Purpus) are described by ultrastr uctural methods. Tapetum degradation appears to be a type of programmed cel l death, with the cellular remnants necessary for pollen development, actin g as products of holocrine secretion. Diagnostic features of apoptosis duri ng tapetum development are: general shrinkage of the whole cell and the nuc lei; condensation of the chromatin at the periphery of the internal nuclear membrane; the enlargement of the endoplasmic-reticulum cisternae to circum scribe portions of the cytoplasm; the persistence of mitochondria together with microfilament bundles until the last stages of tapetal degeneration.